Field of the Invention
The invention relates to a control valve for an injection valve for injecting fuel into internal combustion engines. Such a control valve is known from Published, European Patent Application EP 0 826 876.
For the purpose of supplying fuel to internal combustion engines, increasing use is being made of accumulator injection systems which operate with very high injection pressures. Such injection systems are known as common rail systems (for diesel engines) and HPDI injection systems (for spark-ignition engines). The injection systems are distinguished by the fact that the fuel is conveyed by a high-pressure pump into a pressure accumulator that is common to all the cylinders of the engine and from which the injection valves at the individual cylinders are supplied. The opening and closing of the injection valves are controlled as a rule electromagnetically, possibly also with the aid of piezoelements.
The purpose of the control valve is to effect hydraulic opening and closing of the actual fuel injection valve, that is to say, in particular, to fix the beginning and the end of the injection process exactly in terms of time. The injection valve is intended, for example, to open under control and to close quickly at the end of the injection process. Then, the injection of very small amounts of fuel is to be possible for the purpose of pilot injection before the actual injection with the aid of which the combustion process can be optimized.
In the above-named Published, European Patent Application EP 0 826 876 and in Published, European Patent Application EP 0 778 411, a 2/2 directional valve is used as control valve for a common rail system.